Many inkjet printers use a thermal inkjet process. In a thermal inkjet process, the printheads contain a series of tiny chambers, each containing a heater such as a resistor. To eject a droplet of printing fluid from a chamber, a pulse of current is passed through the heating element causing a rapid vaporization of the ink in the chamber to form a bubble, which causes a large pressure increase, propelling a droplet of printing fluid, such as ink, onto the underlying media. Similarly, in 3D printers, a printhead prints on a layer of powered build material on a movable print support.
The printing process may consume several hundred of watts, which are provided by a power supply.